What is the volume of a certain cube?

For this question, you need to know:
1) A cube has 12 equal length sides, so sum of side length = 12 (length of one side)
2) surface area of a square = length x width (since length = width in a square) = length x length
3) A cube has 6 square faces with equal area, so sum of surface area = 6 (surface area of one side) = 6 (length x length)
4) volume of a cube = length x length x length

So, let's start with statement 1:

Sum of lengths = 36 = 12 (length of one side)
Using algebra, you know that length of one side = 3
Once you have length of one side, you know the volume of the cube. Therefore this is SUFFICIENT.

Eliminate B, C and E.

On to statement 2:
Total surface area = 54
Since there are 6 square faces: 54/6 = area for 1 face = 9
Since area of 1 face of square = 9 = length x length = 3x3
Length of one side = 3
Once you have length of one side, you know the volume of the cube. Therefore this is SUFFICIENT.

Correct answer D.